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#3660
by
Rodal
on 18 May, 2015 16:40
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[...
Thanks Dr, in my world it was thermal. Interesting to note the interference pattern was divided into quadrants and the only image I could locate to explain it was the "diffuser". Soooo, guess no one did a thermal of the DUT?
For what it is worth, I obtained the same image (indistinguishable by eye) with my exact solution for the same mode shape TM212, using spherical ends. It looks like it doesn't make a
perceptible difference for these geometrical dimensions and for this mode TM212 magnetic field whether one has flat ends or spherical ends.
The pattern is due to the need to fulfill the boundary conditions and symmetry conditions for this higher mode. Higher "m" modes have higher number of "cells" symmetrically distributed in the azimuthal "m" direction.
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#3661
by
TheTraveller
on 18 May, 2015 16:48
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...
Shawyer likes to drop bread crumbs, to create a trail for those interested to follow.
Bread crumbs? I feel like a bird ... 
Photo was from 2008 presentation.
Maybe it didn't produce enough thrust and Shawyer produced the final conical 2009 version?
I do note the Rf input is at the top and there is an E field sense output in the middleish of the flat side wall. Or maybe the other way around? Dimensions were given as was input power, which is lower than that published for the final Flight Thruster.
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#3662
by
txdrive
on 18 May, 2015 17:13
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#3663
by
deltaMass
on 18 May, 2015 17:54
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The expectation for measured weight change for Iulian's device is about -0.5 gm-weight (becoming lighter), assuming a temperature rise of the air within the device of about 25oC, and assuming the device volume to be about 6 litres. The mechanism here is based simply on the change in weight of the air within the device. Because the device is not sealed, air can move in and out of it as its temperature changes. The larger the device volume, the larger the expected measured weight change.
I've now calculated the volume to be ~37 litres, and so we need roughly only 1/6th of the previously calculated temperature rise to get the observed weight change - just a few degrees will do it.
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#3664
by
WarpTech
on 18 May, 2015 18:13
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The expectation for measured weight change for Iulian's device is about -0.5 gm-weight (becoming lighter), assuming a temperature rise of the air within the device of about 25oC, and assuming the device volume to be about 6 litres. The mechanism here is based simply on the change in weight of the air within the device. Because the device is not sealed, air can move in and out of it as its temperature changes. The larger the device volume, the larger the expected measured weight change.
I've now calculated the volume to be ~37 litres, and so we need roughly only 1/6th of the previously calculated temperature rise to get the observed weight change - just a few degrees will do it.
I do not believe the air temp went up that fast. And, if it were just a change in air temperature, why would it drop as soon as it's switched off. The air inside can't cool that fast, and the thrust was repeatable with the switch.
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#3665
by
TheTraveller
on 18 May, 2015 18:13
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The expectation for measured weight change for Iulian's device is about -0.5 gm-weight (becoming lighter), assuming a temperature rise of the air within the device of about 25oC, and assuming the device volume to be about 6 litres. The mechanism here is based simply on the change in weight of the air within the device. Because the device is not sealed, air can move in and out of it as its temperature changes. The larger the device volume, the larger the expected measured weight change.
A few points to consider:
1) Cavity is vented to atmo by 2 large holes in the side wall.
2) Expanding / warmer air will exit the cavity via the holes.
3) Thrust appears immediately the magnetron warms up. Heated air would not warm up immediately but do it slowly.
4) Thrust drops to zero immediately the power is off. With heated air, thrust drop would be slow.
The way the thrust reacted to the power switch, suggest to me it is not a heated air effect.
Looking at the solder job of the small end, I doubt it was air tight.
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#3666
by
deltaMass
on 18 May, 2015 18:20
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The characteristics of the heated air will depend significantly on its humidity too.
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#3667
by
TheTraveller
on 18 May, 2015 18:28
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The characteristics of the heated air will depend significantly on its humidity too.
Crank up the volume on the video, You can hear when the magnetron start to buzz and thrust appears immediately there after. When buzz stops, thrust stops. No delay.
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#3668
by
aero
on 18 May, 2015 18:29
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The expectation for measured weight change for Iulian's device is about -0.5 gm-weight (becoming lighter), assuming a temperature rise of the air within the device of about 25oC, and assuming the device volume to be about 6 litres. The mechanism here is based simply on the change in weight of the air within the device. Because the device is not sealed, air can move in and out of it as its temperature changes. The larger the device volume, the larger the expected measured weight change.
I've now calculated the volume to be ~37 litres, and so we need roughly only 1/6th of the previously calculated temperature rise to get the observed weight change - just a few degrees will do it.
How on Earth did you come up with such a large volume? 37 litres is a cubic volume ~33.3 cm on a side. Even 6 litres is a cubic volume 18.17 cm on a side which is quite large.
Do we know the dimensions of the device?
Edit:
Don't bother, my bad. For an example, the Eagleworks Copper Kettle EM thruster dimensions are 27.94 cm OD x 15.88 cm x 22.86cm high.
Equation for volume of a cone frustum is V =(pi*h/3)*(R^2 +Rr + r^2) which gives
Volume = 8836.4908791301 cm^3 or 9 litres.
Edit - I changed the volume, I too had used diameters instead of radii.
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#3669
by
Blaine
on 18 May, 2015 18:31
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The characteristics of the heated air will depend significantly on its humidity too.
Crank up the volume on the video, You can hear when the magnetron start to buzz and thrust appears immediately there after. When buzz stops, thrust stops. No delay.
Both of you could be correct. Although, I have to side with TheTraveller on this one. It would have to be a pretty drastic, and immediate change in temperature which would not have likely happened.
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#3670
by
deltaMass
on 18 May, 2015 18:37
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The expectation for measured weight change for Iulian's device is about -0.5 gm-weight (becoming lighter), assuming a temperature rise of the air within the device of about 25oC, and assuming the device volume to be about 6 litres. The mechanism here is based simply on the change in weight of the air within the device. Because the device is not sealed, air can move in and out of it as its temperature changes. The larger the device volume, the larger the expected measured weight change.
I've now calculated the volume to be ~37 litres, and so we need roughly only 1/6th of the previously calculated temperature rise to get the observed weight change - just a few degrees will do it.
How on Earth did you come up with such a large volume? 37 litres is a cubic volume ~33.3 cm on a side. Even 6 litres is a cubic volume 18.17 cm on a side which is quite large.
Do we know the dimensions of the device?
I miscalculated. I used diameter instead of radius. So divide that by 4 and we're back to about
9 litres . Here's the published dimensions:
http://www.masinaelectrica.com/wp-content/uploads/2015/05/EmDrive-1024x1024.jpg
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#3671
by
Rodal
on 18 May, 2015 18:48
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The characteristics of the heated air will depend significantly on its humidity too.
Yes, humid air will be heated practically instantaneously as microwave heating is not at all due to conduction or convection. Microwave heating is dielectric heating, the water molecule is an electric dipole, hence the water molecules rotate to align themselves with the alternating electric field of the microwaves. However,
as pointed out by Warp-Tech, the tell tale sign is " why would it drop as soon as it's switched off" as the cooling has to proceed by convection (mostly) and conduction at the walls and that will be much slower than the experienced fast drop in measured force as soon as the electricity was turned off. There is no dielectric cooling.
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#3672
by
deltaMass
on 18 May, 2015 18:52
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Not so sure about that. Air is driven out by the pressure differential. As soon as the magnetron is switched off, the driver for that pressure difference vanishes and colder air rushes back in.
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#3673
by
Rodal
on 18 May, 2015 18:54
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Not so sure about that. Air is driven out by the pressure differential. As soon as the magnetron is switched off, the driver for that pressure difference vanishes and colder air rushes back in.
Which has, for
natural convection currents (that is what you propose) a significantly longer time constant. (Relatively slow air speeds compared to forced convection).
Anyway,
I hope he performs an experiment with the EM Drive upside down (and another one with the EM Drive sideways, pointing horizontal) and he let us know the results
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#3674
by
Dortex
on 18 May, 2015 18:58
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The characteristics of the heated air will depend significantly on its humidity too.
Crank up the volume on the video, You can hear when the magnetron start to buzz and thrust appears immediately there after. When buzz stops, thrust stops. No delay.
I'd also like to point out that the thrust drops off the more it's run. If air were a significant contributor to the readings, you'd expect to see it go up (or rather, down) the more the device is run, no?
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#3675
by
TheTraveller
on 18 May, 2015 18:58
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Not so sure about that. Air is driven out by the pressure differential. As soon as the magnetron is switched off, the driver for that pressure difference vanishes and colder air rushes back in.
Sure the driver is gone immediately the power is off but not the heated air/moisture inside the cavity. That takes time to cool via conventional convection / heat xfer to the side walls. Listening to the maggie buzz on & off versus changes in the scale reading is important. Almost no apparent delay.
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#3676
by
TheTraveller
on 18 May, 2015 19:03
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The characteristics of the heated air will depend significantly on its humidity too.
Crank up the volume on the video, You can hear when the magnetron start to buzz and thrust appears immediately there after. When buzz stops, thrust stops. No delay.
I'd also like to point out that the thrust drops off the more it's run. If air were a significant contributor to the readings, you'd expect to see it go up (or rather, down) the more the device is run, no?
Lulian needs to do much longer runs. Those he has done so far are, IMO, way too short. Shawyer did runs of 50 to 90 seconds. But he needs things well matched, the cavity running at resonance, etc or can burn out maggies or other such issues may happen.
I really like this test setup. It tells me Shawyer did it properly.
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#3677
by
deltaMass
on 18 May, 2015 19:06
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The characteristics of the heated air will depend significantly on its humidity too.
Crank up the volume on the video, You can hear when the magnetron start to buzz and thrust appears immediately there after. When buzz stops, thrust stops. No delay.
I'd also like to point out that the thrust drops off the more it's run. If air were a significant contributor to the readings, you'd expect to see it go up (or rather, down) the more the device is run, no?
No, I think. Repeated runs occurring close in time to one another will tend to push up the average temperature. Therefore the
change in temperature of the water vapour in the air, and of the air itself, will be that much less after several consecutive runs.
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#3678
by
Rodal
on 18 May, 2015 19:12
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The characteristics of the heated air will depend significantly on its humidity too.
Crank up the volume on the video, You can hear when the magnetron start to buzz and thrust appears immediately there after. When buzz stops, thrust stops. No delay.
I'd also like to point out that the thrust drops off the more it's run. If air were a significant contributor to the readings, you'd expect to see it go up (or rather, down) the more the device is run, no?
Very interesting observation
This drop off can be explained by Todd's theory. Actually, of all the theories proposed, (Shawyer's, McCulloch's, etc.) that only Todd's theory is able to explain the drop off.
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#3679
by
Dortex
on 18 May, 2015 19:14
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The characteristics of the heated air will depend significantly on its humidity too.
Crank up the volume on the video, You can hear when the magnetron start to buzz and thrust appears immediately there after. When buzz stops, thrust stops. No delay.
I'd also like to point out that the thrust drops off the more it's run. If air were a significant contributor to the readings, you'd expect to see it go up (or rather, down) the more the device is run, no?
No, I think. Repeated runs occurring close in time to one another will tend to push up the average temperature. Therefore the change in temperature of the water vapour in the air, and of the air itself, will be that much less after several consecutive runs.
Not sure if I'm dumb, or you're explaining it poorly. Probably the former. You mean to tell me buoyancy becomes less of an issue because the air around the chamber is getting hotter too?
